![]() Efforts to mitigate this harm, such as fish ladders, have proved ineffective, typically allowing just 3 percent of fish to cross a given dam.Īnother problem: mega-dams rarely live up to the hype pledged by promoters. “Dams trap sediments and are barriers to upstream-downstream movement of aquatic organisms,” explained Kirk Winemiller, an aquatic ecologist at Texas A&M University who was not involved in the study. Fish ladders, like this one installed on the Dalles Dam in Portland, Oregon, United States, don’t work for most fish, so end up providing a false sense of environmental protection. “If we included all the costs honestly, I doubt large hydropower projects would look as good,” said Moran, and would instead lead to the favoring of alternative energy sources.ĭams have been linked to habitat degradation in the areas surrounding reservoirs and on newly created islands, harm to biodiversity and migrating aquatic species, and to negative changes – especially diminished connectivity – in river ecology. Publishing in the Proceedings of the National Academy of Sciences, Emilio Moran and colleagues from Michigan State University in the United States find that the true environmental and social costs of hydroelectric dams have been grossly underestimated. After proliferating in North America and Europe in the mid-20 th Century, hydroelectric fell out of favor there in the 1970s and more dams are being removed than constructed nowadays.īut hydroelectric development didn’t stop, it moved location – thousands of dams have been built in developing nations since the 1970s, with many more planned. Hydroelectric power accounts for about 70 percent of the world’s renewable energy supply, yet large dams have been widely criticized for their disappointing energy outputs, short lifespans, and negative impacts on local ecosystems and people. ![]() ![]() Large hydroelectric dams are not worth the environmental and societal costs, and their benefits will continue to dwindle further as the climate changes, analysts argue. This Amazon mega-dam has produced massive floods upstream in Brazil and Bolivia, killing livestock, flooding rural villages and generating an international political crisis. Image courtesy of Santo Antonio Energia. The Santo Antionio dam on the Madeira River in Roraima state, Brazil, went into operation in 2012. Wind and solar offer other alternatives to mega-dams. Instream Energy Generation (IEG) uses clusters of small turbines, enabling fish and sediments to pass freely while generating power.
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